1. Field of the Invention
The present invention relates in general to the field of antibody mimetics, specifically to multimeric scaffolds based on the fibronectin type III (Fn3) domain useful, for example, for the generation of products having novel binding characteristics. In particular, the invention relates to TRAIL R2-specific multimeric scaffolds derived from the third FnIII domain of human Tenascin C and their use for TRAIL R2 receptor detection and modulation of TRAIL R2-mediated function such as treatment of cancer and other disorders.
2. Background Art
Biomolecules capable of specific binding to a desired target epitope are of great importance as therapeutics, research, and medical diagnostic tools. A well known example of this class of molecules is the antibody. Antibodies can be selected that bind specifically and with affinity to almost any structural epitope. However, classical antibodies are structurally complex heterotetrameric molecules with are difficult to express in simple eukaryotic systems. As a result, most antibodies are produced using complex and expensive mammalian cell expression systems.
Proteins having relatively defined three-dimensional structures, commonly referred to as protein scaffolds, may be used as reagents for the design of engineered products. One particular area in which such scaffolds are useful is the field of antibody mimetic design. Antibody mimetics, i.e., small, non-antibody protein therapeutics, capitalize on the advantages of antibodies and antibody fragments, such as high affinity binding of targets and low immunogenicity and toxicity, while avoiding some of the shortfalls, such as the tendency for antibody fragments to aggregate and be less stable than full-length IgGs.
These drawbacks can be addressed by using antibody fragments created by the removal of parts of the antibody native fold. However, this often causes aggregation when amino acid residues which would normally be buried in a hydrophobic environment such as an interface between variable and constant domain become exposed to the solvent. One example of a scaffold-based antibody mimetic is based on the structure of a fibronectin module of type III (FnIII), a domain found widely across phyla and protein classes, such as in mammalian blood and structural proteins.
TRAIL (tumor necrosis factor-related apoptosis-inducing ligand, also referred to in the literature as Apo2L and TNFSF10) belongs to the tumor necrosis factor (TNF) superfamily and has been identified as an activator of programmed cell death, or apoptosis, in tumor cells. Both the membrane-bound and soluble forms of TRAIL are able to trigger apoptosis via interaction with TRAIL receptors located on target cells. In humans, five receptors have been identified to have binding activity for TRAIL. Upon binding of TRAIL to TRAIL R1 or TRAIL R2, caspase-related cell death is triggered. In light of this cell death activity, TRAIL-based therapeutic approaches are being pursued. Several therapeutic approaches based on TRAIL or TRAIL R1 or R2 human agonistic antibodies have been developed, however, TRAIL has a very short life, it binds to decoy receptors, and the large size of antibodies can limit their tumor penetration. Accordingly, there is a need for novel molecules that can bind to TRAIL receptors, pharmaceutical compositions comprising those molecules, methods for screening for such molecules, and methods for using such molecules in the therapeutic treatment of a wide variety of cancers.
Citation or discussion of a reference herein shall not be construed as an admission that such is prior art to the present invention.